Self-propelled vehicles which are operable on either roadways or highways are widely known and used in the rail industry. For instance, U.S. Pat. No. 3,019,742 discloses a universal mobile unit for self propulsion on either highways or railways which embodies a source of power for motivation of various instrumentalities and one in which is so constructed and arranged as to provide for the selective attachment, support and conveyance of such various types of maintenance equipment so the one unit may be universally applicable for carrying out a wide variety of maintenance and construction operations. Moreover, such inventions are embodied in units which also include means by which the railway wheels and/or the roadway engaging wheels may be selectively rotated for propulsion or by which they may be synchronously rotated together to provide dual traction. Such prior art units also provide for the application of roadway tires to a railway rail whereby the inherent superior tractive effect of conventional rubber treads may be applicable in the movement of the unit on railway rails while the railway wheels engage the rails to preclude lateral displacement of the unit from the rails.
There are also prior art units such as the Fairmont-Series 4072 Heavy-Duty Guide Wheel equipment which is designed for crane carriers and special-purpose heavy-duty truck applications. The tandem bogie-type guide wheel unit features coil spring suspension, brakes on all wheels, positive mechanical latches in both rail and roadway positions, and fill hydraulic control of raising and lowering the guide wheels. Units such as the Fairmont-Series 4072 require the vehicle to maneuver to a position parallel to the railway or roadway to make the desired conversion.
However, prior art road and rail vehicles lack the ability to allow the roadway to railway conversion absent placing the vehicle parallel to the desired railway or roadway. Moreover, narrow road crossings present prior art vehicles with increasingly difficult maneuverability problems. Accordingly, there exists a need for a vehicle which has improved operational characteristics which will not require placing the vehicle in the parallel position. Moreover, there exists a need for a vehicle which has improved operational characteristics thereby allowing it to convert from the roadway to the railway position at narrow crossings which would create conversion problems otherwise.